These teachings relate generally to wireless communication terminals or mobile stations, such as powered cellular telephones, and more specifically relate to techniques to optimize the power consumption of portable, battery powered mobile stations.
An important aspect of the design and operation of battery powered mobile stations, such as cellular telephones and personal communicators, is the optimization of the power consumption. A direct result of the optimization of the power consumption is an increase in both the standby and talk times of the mobile station between battery recharging operations, both of which are readily experienced by and apparent to the user.
One significant power consuming operation of mobile stations is a requirement to make measurements of signals received from base stations or base sites of neighboring cells when operating within a currently serving cell. In a typical case the mobile station periodically receives a list of neighboring cells from the serving cell base station and then makes measurements, such as received signal strength measurements for radio channels from the neighboring cells. The results of these signal strength measurements are reported back to the base station of the serving cell. These signal strength measurements are useful in determining candidate cells for handoff and reselection purposes. As can be appreciated, these received signal measurement and reporting operations consume some amount of mobile station power.
It is known to reduce mobile station power consumption by detecting the motion of the mobile station using GSM (Global System for Mobile Communications) measurements, and reducing the number or frequency of adjacent cell measurements based on the detected motion. In this case the underlying rationale is that if the mobile station is stationary or moving only slowly that the previously made neighbor cell measurements most likely remain valid, and need not be re-measured.
It is also known in a dual mode wide bandwidth code division multiple access (WCDMA)/GSM mobile station to reduce the power consumption by optimizing finger (correlator) allocation in a multi-finger rake receiver, in addition to reducing the number of neighbor cell measurements based on a detected motion of the mobile station.
In U.S. Pat. No. 6,067,460 by S. Alanara, J. Ranta, H. Pirila and H. Jokinen the present inventor and others describe a mobile station that when in a DCCH camping state monitors its assigned page frame. After making RSSI and possibly also Bit Error Rate/Word Error Rate (BER/WER) measurements the mobile station monitors the rate of change of the RSSI. If the rate of change is small and remains so, the mobile station is assumed to be in a stationary state. After determining that it is stationary, the mobile station may give an audible alert and/or display a message to request the user to confirm that the mobile station is (and will remain) stationary. When in the stationary state the mobile station inhibits making neighbor channel measurements for DCCH reselection. The mobile station continues to monitor its assigned page frame within an assigned digital control channel and to measure its own channel RSSI and possibly also the BER/WER. If these values subsequently indicate that the mobile station is no longer stationary, the mobile station immediately resumes all neighbor channel measurements.
In U.S. Pat. No. 6,108,553 by M. Silventoinen, T. Rantalainen, M. Raitola and J. Ranta the present inventor and others describe a method for determining the position of a mobile station, a positioning system and a mobile station. In this approach a mobile station receives signals from at least two base stations and determines time differences of the clocks of the received signals. The mobile station sends information about the time differences to a positioning service center of the mobile communication system which then calculates the position of the mobile station on the basis of the time difference information and base station coordinates and clock information. Using this method it is possible to measure signals with signal strengths that remain below the minimum decoding level. It is also possible to measure bursts containing short training sequences to improve timing measurement accuracy and measuring speed. The time difference measurement results obtained are transmitted from the mobile station to a base station by encoding the results in a signalling channel (SACCH) burst. The method enables quick position measuring at short intervals without substantially increasing the load on the mobile station or on the air interface.
Although well-suited for their intended applications, it is desirable to provide even further power savings and power consumption optimization in those types of mobile stations that also include a power consuming Global Positioning System (GPS) reception and position location calculation capability. Previously, the power consumption of each of the cellular-based and GPS-based mobile station systems were addressed separately without any cooperation between these systems.
The foregoing and other problems are overcome by methods and apparatus in accordance with embodiments of these teachings.
In accordance with these teachings a mobile station has two location determination systems that support the power saving functions of each other. These two systems are the cellular system, which may contain multiple modes such as GSM/WCDMA, and the GPS used for positioning services only. Information regarding motion of the mobile station is obtained from both systems, and the power consumption of both the cellular and GPS systems are reduced in accordance with a combination of the obtained motion-related information.
Disclosed is mobile station system and a method for operating the mobile station to reduce the power consumption thereof as a function of a presence or absence of motion, and as a function of a duration of a period over which motion above a motion threshold is not detected. The system includes cellular system reception circuitry and circuitry implementing a cellular system positioning function and a satellite-based positioning function. The circuitry includes a controller that operates in accordance with a stored program for obtaining and combining a plurality of received signal-derived parameters of the cellular system, a position of the mobile station derived from the cellular system positioning function, and a position of the mobile station derived from the satellite-based positioning function to derive a value that is indicative of a presence or absence of motion of the mobile station. The controller compares the value to a motion threshold and, when an absence of motion is detected, the controller is responsive for reducing the power consumption of the mobile station by selectively decreasing the usage of the mobile station cellular system reception circuitry, the cellular system positioning function and the satellite-based positioning function.
In a non-limiting CDMA-based cellular system embodiment the mobile station cellular system reception circuitry includes a PN code searcher and PN code fingers that are allocated in a rake receiver.
In an illustrative embodiment the received signal-derived parameters of the cellular system include received signal parameters for a currently serving cell and for at least one adjacent cell, and include one or more of a received signal strength indicator (RSSI), a signal to interference ratio (SIR), a received signal code power (RSCP), a block error rate (BLER) and a bit error rate (BER).